One lesson of the 2006 vote was so obvious that Ron Brownstein of the Los Angeles Times was able to write about it two days before the election: the return of the swing voter. Karl Rove's strategy of mobilizing a conservative Republican base while ignoring the flippable voters in the middle "lay shattered in pieces," exactly as pollster Stan Greenberg told Brownstein it would.

It is with a sense of relief that we welcome back the swing voter. The craziness is ending. The arc of politics again points toward the center. David Broder can exhale.

And yet, before we hoist the swing voter up on a chair and parade him around the room, let's take a moment to point out some of his uglier qualities. And let's have a few words of praise for the strategy of mobilizing the base and even for dear old Karl Rove.

Remember what it was like when elections were about swing voters and no one else? It wasn't long ago and it wasn't pretty. The election of 1996, the only presidential election in which turnout fell below 50 percent, was the ultimate swing-voter election. Both parties assumed that the electorate was a fixed quantity, and that the payoff for flipping a voter in the middle far exceeded that of trying to drag a nonvoter to the polls. "Don't waste time on people who don't vote" was every campaign consultant's mantra at that time.

That created a politics that was every bit as detached from the reality of most Americans' lives as the recent focus on the partisan base. That was the era that brought us E.J. Dionne's Why Americans Hate Politics, Robert Putnam's Bowling Alone, and other attempts to plumb the chasm between Americans and their public life. Young people were enthusiastically volunteering, but nothing could persuade them that voting mattered a bit. This was the era of the trivial "micro-initiatives" of middle-period Clintonism.

The nicknames that pollsters developed for the swing voters of this era -- all those "soccer moms" and "office-park dads" -- remind us of the narrow perspective of these campaigns. They focused largely on a constituency of white employed homeowners, whose politics was internalized and anxious. Allergic to taxes, they were nonetheless protected from the big economic forces that were destroying Rust Belt cities and rural communities. Socially liberal, they were also environmentalists, but in a safe, middle-class way, concerned about open space in their communities and about oil drilling in the Arctic.

In fact, some of the dysfunction in the Democratic Party that is often attributed to the interest and identity groups on the party's left actually has more to do with the obsession with swing voters. If you wonder, for example, why the Democrats of the late 1990s had a lot to say about reproductive choice and not much of an economic message, it was not because of feminist influence. Rather, they were transfixed by polls showing that in key states such as Ohio, a decisive 4 percent to 6 percent of voters were well-off Republican-leaning women who were strongly pro- choice and could be pulled away by a reminder of the threat to Roe v. Wade. As Democrats chased after these narrow targets, they created the impression of a party that cared about little else. Such a politics also led to historically weak political parties, because no effort was made to draw these voters into a broad and lasting coalition, but merely to "swing" them to one side for the moment.

I doubt that Karl Rove's insight was that "there are no swing voters." There are always swing voters. What Rove discovered was that it might not be as much of a waste of time and money as previously thought to go after people who hadn't voted -- and, therefore, one could worry less about the electoral middle. He was right -- there was a vast untapped potential vote out there -- and his insight was so radical and disruptive that it dominated politics for the five years that it took Democrats to understand it. But like a hedge fund genius with a brilliant strategy, he took it too far, didn't recognize its limits, and never diversified his portfolio.

The insight lives on, however. The Democratic victory was built on swing voters and the base. Almost every category increased its Democratic vote, from white suburban men to African Americans and unmarried women. The election raises the possibility of a future in which Rove's insight is normalized, in which stronger parties seek to build and expand their bases while also reaching into the center. If they do both, they will create a politics that is more balanced and relevant, one in which the economic pressures on low-income families and the anxieties of the middle class are both heard. If so, let's send a thank-you note to Karl Rove, wherever he is by then.